A light emitting diode (LED) is a kind of a P-N junction diode and is a semiconductor device using an electroluminescence which is a monochromatic light emitting phenomenon when a voltage is applied to forward direction. The wavelength of the light emitted from the light emitting diode is determined by the badgap energy (Eg) of a material used. At the beginning of the light emitting diode technique, light emitting diodes capable of emitting infrared and red light have been developed. Researches on a blue LED has begun in full-scale after founding that a blue light might be generated when using GaN by Nakamura at Nichia Chemistry in 1993. Since white light may be obtained through combining red, green and blue, the development on the GaN-based blue light emitting diode along with already developed red and green light emitting diodes, enabled the accomplishment of a while light emitting diode.
Recently, as the demand on the blue wavelength light emitting diode increases, the demand on a GaN thin film is also increased from day to day. In order to increase the efficiency of the light emitting diode, various methods have been used.
As another expedient to increase the light emitting efficiency, a vertical type light emitting diode increasing the light emitting efficiency by removing the substrate gets the spotlight. The vertical type light emitting diode may be obtained by a laser lift off (LLO) method in which a nitride semiconductor deposited substrate is exposed to a laser and the substrate and the nitride semiconductor are separated, or by a chemical shift off (CLO) method in which a substrate is melted to separate the substrate and the nitride semiconductor. Through the methods, much effort has been made to improve an adverse influence to the nitride semiconductor and to improve defects concerning complicated processes. However, a method giving a high efficiency to a desired degree has not been accomplished yet.